vscroll/dist/esm2015/classes/buffer/checkCall.js

Virtual scroll engine

import { Direction } from '../../inputs/index';
export class CheckBufferCall {
  constructor(context, logger) {
    this.context = context;
    this.logger = logger;
  }
  fillEmpty(items, before, after) {
    if (!items.length) {
      this.logger.log('no items to fill the buffer; empty list');
      return false;
    }
    if (!Number.isInteger(before) && !Number.isInteger(after)) {
      this.logger.log('no items to fill the buffer; wrong indexes');
      return false;
    }
    this.logger.log(() => `going to fill the buffer with ${items.length} item(s)`);
    return true;
  }
  insertInBuffer(predicate, before, after) {
    const index = Number.isInteger(before) ? before : (Number.isInteger(after) ? after : NaN);
    const found = this.context.items.find(item => (predicate && predicate(item.get())) ||
      (Number.isInteger(index) && index === item.$index));
    if (!found) {
      this.logger.log('no items to insert in buffer; empty predicate\'s result');
      return NaN;
    }
    return found.$index;
  }
  insertVirtual(items, index, direction) {
    if (!items.length) {
      this.logger.log('no items to insert virtually; empty list');
      return false;
    }
    const { firstIndex, lastIndex, finiteAbsMinIndex, finiteAbsMaxIndex } = this.context;
    if (index < finiteAbsMinIndex || index > finiteAbsMaxIndex) {
      this.logger.log(() => 'no items to insert virtually; ' +
        `selected index (${index}) does not match virtual area [${finiteAbsMinIndex}..${finiteAbsMaxIndex}]`);
      return false;
    }
    const before = direction === Direction.backward;
    if (!(index < firstIndex + (before ? 1 : 0) || index > lastIndex - (before ? 0 : 1))) {
      this.logger.log(() => `no items to insert virtually; selected index (${index}) belongs Buffer [${firstIndex}..${lastIndex}]`);
      return false;
    }
    this.logger.log(() => `going to insert ${items.length} item(s) virtually`);
    return true;
  }
}
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